1. Field of the Invention
The present invention relates to a mobile radio-receiver system, more particularly, to a mobile radio-receiver system applied to a radio-receiver set mounted on a vehicle, wherein a reproduction characteristic of a reception signal having noise superimposed thereon is improved.
The present invention also relates to a sound reproduction system, such as an FM radio-receiver unit, including such a radio-receiver system.
2. Description of the Related Art
In a radio-communication system, a radio-reception signal has noise superimposed thereon, and thus the radio-receiver unit must eliminate the affect of this noise to provide a high quality reproduction signal. As a typical example thereof, a signal received at a radio-receiver of a mobile radio-communication system is greatly affected by noise superimposed thereon, according to the time and place at which the signal is received.
In a mobile sound reproduction system installed in a vehicle and including a mobile radio-receiver system, more specifically, in an FM radio-receiver set installed in an automobile, the noise in a received signal is mainly due to standing waves and multi-paths. A diversity system is able to eliminate the affect of the standing-wave noise, and a high pass filtering and/or signal prediction means are able to obviate the affect of the multipath noise. Nevertheless, the diversity system can not eliminate the multipath-noise, and the high pass filtering and/or signal prediction means can not obviate the standing-wave noise. Accordingly, to reproduce the received signal with a high quality, i.e., to reproduce speech or music through the radio-receiver set while maintaining the quality of the original transmitted sound, all noise must be effectively eliminated by the mobile radio-receiver system.
Many approaches have been made in attempts to eliminate the affect of noise, but these prior art methods can not provide a high quality reproduction signal. The prior art methods will be described later in more detail with reference to specific examples and the drawings.